1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method.
2. Description of the Related Art
Conventionally, in an image forming process of a full color copy mode by digital color copying machines, a copying process related to four basic colors of cyan (C), magenta (M), yellow (Y), and black (Bk) is performed, and these colors are output on a sheet of transfer paper. Furthermore, when performing a copying process of a monochrome copy mode, a monochrome image is output on a sheet of transfer paper in a single copying process. Accordingly, in copying machines of this type, amounts of toners used in a full color mode and a monochrome mode largely differ from each other, and costs of copying for users of the copying machines largely change. Furthermore, depending on the modes, the images output on the sheets of transfer paper largely differ from one to the other, and thus the users need to be careful in switching operation modes between the color mode and the monochrome mode and must switch the operation mode in accordance with the type of image (original image) represented on an original as appropriate. To solve the burden of this type of operation mode switching, there is a technique for automatically determining whether an original image is a chromatic image or an achromatic image (color determination) and automatically switching, in accordance with the determination result, the operation mode of the copying machine (automatic color selection: ACS) is known. However, if the color determination is erroneous, in particular, if an achromatic image is erroneously determined as a chromatic image, the copying process is performed using the four CMYK colors. Accordingly, not only colors of an image output on the sheet of transfer paper become different from the color expected by the user but also the cost and the time required in the copying increase. Therefore, there is a need to perform the determination with high accuracy.
In recent years, digital color copying machines are not only used on their own, their compatibility with other devices that handle digital image data has been enhanced, and they are integrated with facsimile functions, printer functions, delivery scanner functions, or the like, and called multi function printers (MFP). Furthermore, because capacities of recording media, such as hard disc drives (HDDs) have increased and costs thereof have decreased, large-capacity storage media are starting to be used in MFPs. In the large-capacity storage media, it is possible to store original images scanned once or to store images received from other media. The stored images are readable again and reusable for purposes different from those at the time of the storage. For example, if an original image is scanned by a scanner and an image sent by delivery scanner functions is stored in an HDD, it is possible, without re-scanning the original image by a scanner, to deliver image data to an MFP different from the MFP that scanned the original image or to output the image data on a sheet of transfer paper anew. Furthermore, an original image may be output with equal-magnification upon scanning and thereafter, the same original image may be output enlarged at a magnification such as of 200%.
An image-region separation process of determining whether such an original image is a text region or a picture region and outputting a result of the determination as an image-region separation result, or a color determination process of determining whether the original image is a chromatic image or an achromatic image as described above may be performed. In such a process, processes are switched such that an appropriate process is performed depending on the result of the determination, and thus the process needs to be performed before filter processing, color-correction processing, and gamma processing. For example, Japanese Patent Application Laid-open No. 2007-251835 discloses a technique for simultaneously storing image data and appendant information (e.g., an image-region separation result) on the image data. Accordingly, while maintaining the quality of the image data stored in a storage device, it is possible to effectively utilize the capacity of the storage device. Furthermore, Japanese Patent Application Laid-open No. 2002-369012 discloses a technique for holding a plurality of pairs of image data and a color determination result.
However, to store data scanned by a scanner in a highly reusable manner as described in Patent Application Laid-open No. 2007-251835, the image data and the appendant information need to be stored such that a user is able to reuse them by an arbitrary method. As described above, a user of an MFP needs to be careful in the switchover between the color mode and the monochrome mode and to appropriately switch the modes in accordance with the type of the original. Accordingly, an ACS function of automatically switching an operation mode of a copying machine in accordance with a result of color determination is required when reusing. When an MFP is used as a copying machine, there is not only a problem that an image copied on a sheet of transfer paper largely differs from an image expected by a user, but also a problem that, if an achromatic image is erroneously determined as a chromatic image, the cost required for the copying increases and productivity decreases. However, when an MFP is used as a delivery scanner, although only information on brightness is fundamentally needed for an achromatic image, information on colors may be needed to increase the file size, which may suppress the capacity of an HDD drive included in a PC of a user because of determining the achromatic image as a chromatic image. Accordingly, there is a need to store a color determination result as appendant information of the stored image. According to Japanese Patent Application Laid-open No. 2007-251835, the color determination result is stored as appendant information of the stored image. As occasions of use for various purposes by users increase, the purposes of a user in the storing of an image and in the reusing of the image tend to differ from each other. Accordingly, a color determination result stored as appendant information may be different from the intention of the user.
By using the technique disclosed in Japanese Patent Application Laid-open No. 2002-369012, it is possible to store a pair of image data and a color determination result according to multiple modes of reuse. However, even when only a case is envisioned in which a magnification is changed for reusing, saving images corresponding to all magnifications that are specifiable with respect to one original requires a large-capacity HDD drive to be installed in the MFP. Accordingly, a conceivable approach is to recheck the determination when an image size desired by a user to be finally output by reusing a stored original image is determined, even if a color determination has been performed on the entire original image upon scanning of the original image. If the purposes by a user differ between the time of storing the original image and the time of reusing the original image, the color determination that has been performed upon the scanning of the original image may often be unreliable.
For example, if a magnification of an original image is changed by, for example, enlarging the original image and the enlarged image is output or if only a part of the original image is output, only the part of the original image that has been subjected to color determination upon scanning of the original image is output. At this time, because the entire original image is the area to be determined in the color determination upon the scanning of the original image, for an image to be output, which is a part of the entire original image, the color determination result is unreliable. Although the color determination of determining the attribute of whether the image is an achromatic image or a chromatic image, as a feature related to colors of the image, has been described as an example, the same description can be made for a case in which a determination of an attribute, as a feature related to an image quality of the image, which is a type of the original, such as of determining whether the original is a text original, a photographic original, a text and photographic original, or the like is performed. Specifically, even when an original as a whole is a text and photographic original, if only a part of an original image is output, only text may exist in that part. Accordingly, the determination of the original type upon the scanning of the original image may be unreliable.